anv/blit2d: Remove sampler from pipeline

anv/blit2d: Remove sampler from pipeline

Since we're using texelFetch with a sampled image, a sampler is no
longer needed. This agrees with the Vulkan Spec section 13.2.4
Descriptor Set Updates:

sampler is a sampler handle, and is used in descriptor updates for types
VK_DESCRIPTOR_TYPE_SAMPLER and VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER
if the binding being updated does not use immutable samplers.

Signed-off-by: Nanley Chery <nanley.g.chery@intel.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>